The present disclosure relates to a wind turbine particularly, but not exclusively, suited for generating electricity. More particularly, the disclosure herein describes a wind-driven turbine intended for very large rotor sizes, such as for rotor sizes greater than 100 meter.
The field of multi-megawatt wind turbines has experienced an important development over the last years. In particular, the size of multi-megawatt wind turbines is doubling approximately every five years. This development targets lower cost of electricity (i.e., cents per kWh) which can be achieved by providing higher energy conversion. In order to reach higher energy conversion, the aerodynamic efficiency of the turbine may be improved or the rotor size may be increased. The latter is a straightforward solution to increase energy conversion in wind turbines.
In particular, by increasing the rotor size, the swept area is increased and, consequently, also the power output of the wind turbine. However, increasing the size of the rotor usually involves a dramatic increase in the size of the machinery. Particularly problematic is the implementation of the nacelle in large-scale wind turbines, due to its high mass. A further problem is the high load on the pitch and yaw bearings due to bending moments or thrust forces. In the case of large-scale wind turbines, this load can override the charging limit of the bearings. Moreover, large-scale wind turbines usually involve high dynamic loading of the rolling elements in the bearings. The blade-to-tower clearance might also be an issue in the design of large-scale wind turbines.